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My MC30's are back from repair, and mating quite nicely with the La Scala's.
Hope everybody else has a great weekend also.
Follow Ups:
I'm a huge fan of the MC30. We briefly had in at the same time a pair of La Scalas, a pair of MC30s, and a pair of Atma-Sphere M50 amps. The La Scalas are the only speaker in our shop that the Atma-spheres sounded better on (only slightly, though).
I'm fairly convinced that if people who have had negative experiences with La Scala's could sit in my room and listen to them with the MC30's the combination of room/amps would change some minds, at least temporarily.
Mine are a bit of a mismatch with one not have a McIntosh logo and no holes to mount one unless it had been glued.
They're the perfect match for Altecs as well.
-Rod
I use a pair of MC40's with my 604-8g and I love the combo. I can't believe I've been listening to these for 15 years.
I'd heard of the MC-40s and see that they replaced the 30s and are rated for 10 more watts. From the pics, they look about the same as the MC-30s with the same tubes except the 5U4. Is the difference tube versus SS rectification?
-Rod
The single biggest difference is the vacuum rect for the 30 power supply compared to the silicon voltage doubler for the 40. This alone probably accounts for the 10W power difference. The 40 also incorporates an additional feedback loop from the cathodes of the finals to cathodes of the 12AX7 drivers (g1 of finals). Schematics for the latest version of the 30 also show this additional feedback loop but I've never seen an actual 30 with it. There are many other minor differences such as a hum pot on the 30 vs none on the 40, bias supply circuit etc. Also, Mac made many changes during production runs so schematics don't always match reality.
I have a 240 for a second system, and while I adore it, there is a definite difference in it's sound vs. the 30's that I chalk up to SS vs. tube rectification. It's the latter which accounts for the incredible midrange magic on the 30 that makes vocals especially hauntingly good, especially on a speaker like Klipsch La Scala's. I find myself looking up more from whatever work I'm doing when music is playing as I hear things, phrasing or whatever that I never heard before.
Obviously, 30s are mono, 240 is stereo so PS sharing is present in 240. There's also the addl feedback loop in the 240 that most likely isn't present in the 30. Hopefully since your amps are in frequent use, critical passives have been replaced, esp but not limited to the bumblebees. Unless the passives are the same for each amp, there's another possibility for sonic differences betw them. Further confounding this is the fact that Mac's unity coupled designs are inherently high feedback with nested positive and negative loops (if stock) which may diminish differences in passive characteristics. From my perspective, it's difficult to point to any one or two physical difference betw the amps as the cause of sonic differences.
Edits: 02/15/22
Both amps have been completely restored but you're right there are other differences that would account for sonic differences.
Mine came with a hum pot or a bias pot, though I recall John saying it was for bias. In any case, I think he might have done it for the previous owner and didn't like it, so I left them for him to sort it out.I know the bias is dead nuts and it's over 30 watts after he replaced a few tubes with Amperex.
I'm pretty good with computers, but borderline dangerous on schematics.
What I wonder is how the same driver tubes do stereo on the 240 versus the sames tubes for a mono block. It seems like I have twice as many per amp. My wild ass guess is the tubes half two halves and only one is used for the 30s.
-Rod
Edits: 02/14/22
If you don't count the rectifier the tube complement /count of a 30 and 40 are the same. A 240 almost doubles the count of the 40. The difference is the input 12AX7. In a 40 (30 too), only one of the two triodes is used the other is disabled. On a 240 one of the triodes is used for the right channel and the other for the left. So the tube count for a 240 is (2X40)-1 or 11 vs 6.
Ok, I got confused and had been looking at an MC-225 which has two 12BH7s and has two 12AU7s instead of the two 12AX7s on the MC-30. Obviously, it completely different.
-Rod
The 225 dispenses with the 12AX7 cathode follower driver so it has two fewer tubes than a 240 (or a 275). The 225 is one sweet little amp. . . arguably Mac's best sounding of the vintage series. Too bad power output is limited.
Rod M, the lab I worked in as a grad student had a number of MC 60s and several VOT A-500s. I borrowed a pair for listening at home. They were particularly good for the brass in Aida.
db
As you might notice mine are not cosmetically matched either. As close as I could get.
I'm not as cosmetically perfect either.
It's the iron that counts. You could pay far more for perfect looks that may still need restoration. ;)
-Rod
About to turn 65 my cosmetics ain't so grand either, but a hell of lot better after various restoration over the last few years then before that.
As for the amps, after a more detailed restoration they are sounding better then ever in addition to looking very good. I'm a happy fella.
Hello sberger,they look great. I have a pair myself but I need to get them some repair work. Can you suggest a repair shop ? I live in the southeast US. Thanks.
Finding an expert is hard as there aren't many left. John had restored mine for the guy that I bought them from and John insisted on checking them out completely because his client was known to mess around. ;)
The problem is shipping. It's likely $200 each way since they're heavy. If you were around LA, he'd be your guy.
-Rod
I'll keep him in mind as I'm in the San Francisco area, so it would certainly be cheaper then sending back East after my warranty with Audio Classics expires.
Which means hopefully I won't need any repair for at least another year.
Not long ago it would've been Mac approved Terry DeWick in Knoxville, but he's now retired. Since I'm on the West Coast I'm not familiar with other places around there although it might be worth contacting Terry or his partner Tom Manley to see if they can recommend somebody in the event you don't get suggestions here. I've linked to their web page.
These were had through Audio Classics in NY who are McIntosh approved. Not long after purchase they each developed issues and needed to be sent back for repair. Just got them back yesterday and so far so good. Or so great. They really sound fantastic.
Good luck with yours.
Thanks for the info. Yes Terry DeWick was my go-to man for repairs but has retired. I am not a fan of Audio Classics at all. Like you I have purchased from them and would have to send the unit back as soon as I got it. I understand that there is another place in the upper mid west that might be where I send them to. I hate to see the shipping cost hahaha...But these Mc30's are truly wonderful and need some tender loving care. I hope you will enjoy yours. Thank you again my friend.
Yes unfortunately AC has not been as top notch as I would've liked. I think one has to buy from them without assuming too much, and be very clear as to what their expectations are. I've had good luck with them in the past and perhaps took too much for granted. Live and learn.
Nice indeed!
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